Chronic Lymphocytic Leukemia With Leptomeningeal Involvement Presenting as an Acute Encephalopathy.

Introduction Chronic lymphocytic leukemia (CLL) is the most common adult leukemia in Western countries. Extramedullary involvement in the central nervous system (CNS) is a rare complication of the disease, and less than 200 cases have been reported. We report a case of leptomeningeal involvement of CLL that presented as an acute encephalopathy. Case presentation A 76-year-old man with treatment-naïve, Rai stage 0 CLL presented with altered mental status. Cerebrospinal-fluid studies, including flow cytometry, confirmed the leptomeningeal involvement of the previously diagnosed CLL. Surveillance imaging and lab studies showed no evidence of disease progression or Richter's transformation. One-time intrathecal methotrexate resulted in transient improvement of his mental status. Conclusion CLL patients with new-onset neurologic manifestations should be evaluated for the CNS involvement of the neoplasm via brain imaging and cerebrospinal-fluid flow cytometry. This CNS involvement of CLL is associated with poor clinical outcomes. Intrathecal treatment with methotrexate, cytarabine, and steroid may improve neurologic symptoms.